I’ve used Schaller strap locks on a number of guitars and basses now. With the S-lock updates almost all my past issues were fixed, but one still remains: a 10mm thread doesn’t really fit in a 6-7mm strap hole. A bit of a shove gets it to fit, then cranking down on the nut works but the strap always ended up warped with the slot splayed open.

Rather than just put up with this I decided to do something about it and ordered a 10mm leather punch.

The idea was to enlarge the strap hole so the lock fits neatly removing the need to force the leather. This should make it look nicer and also stop the small splits you normally get.

This is what a strap normally looks like after fitting the S-lock. The leather is miss shaped and the slot has splayed open. If you undid the nut you would see 1 or 2 tiny tears around the lock barrel.

As the strap was used when I punched the hole I decided to keep the new hole central but remove as much of the use damage as possible. On the front this was easy to do as the strap kept its shape. On the tail this meant 2 goes whilst pushing the strap inwards to keep its factory shape.

Not much material is actually removed, maybe a 1mm band of leather.

And with this done the lock barrel fits perfectly in the new larger hole, no warping no splaying.

Doing up the nuts after this mod is far easier. No having to compress the leather to squash down the ripples, or struggling to keep the lock straight to the strap. Just turn the nut down slowly and firmly.

As I’d used this strap a fair bit when I did this you can see the leather still splayed a little but nothing like as bad as above. I suspect if this was done on a new strap there would be no warping or splaying at all.

Whilst the punch isn’t an everyday item, it’s also pretty cheap. So long as you only punch into something like a cheap plastic IKEA chopping board it won’t get damaged, and so will last for a lot longer than a few straps.